Display screen or portion thereof with transitional graphical user interface



FIG. 1 is a front view of a display screen or portion thereof with transitional graphical user interface showing the first image in a sequence.

FIG. 2 is the second image thereof.

FIG. 3 is the third image thereof.

FIG. 4 is the fourth image thereof; and,

FIG. 5 is the fifth image thereof.

The appearance of the transitional image sequentially transitions between the images shown in FIGS. 1-5. The process or period in which one image transitions to another image forms no part of the claimed design.

The outermost broken line rectangle illustrates a display screen or portion thereof and forms no part of the claimed design. The remaining broken lines in the drawings, including all text shown, illustrate portions of the graphical user interface and form no part of the claimed design. 

CLAIM The ornamental design for a display screen or portion thereof with transitional graphical user interface, as shown and described. 